Comparison of process stability in methane generation from palm oil mill effluent using dairy manure as inoculum

The potential of methane production in a continuously stirred tank reactor (CSTR) was investigated using dairy manure as inoculum at pH 6.8 and 37 degrees C temperature in this study. Two identical anaerobic bioreactors namely CSTR1 and CSTR2 filled with palm oil mill effluent (POME) as a carbon source were used. CSTR1 was not added with the inoculum, while CSTR2 was added with dairy manure as inoculum. Both the reactors were allowed to run for 5 days (d) in batch condition at hydraulic retention time (HRT) 10 d. The CSTR(2)produced 0.85 L/d gas yield and 59% methane content compared to 0.39 L/d gas yield and 20% produced in CSTR1, respectively. A better chemical oxygen demand (COD) reduction percentage of 48% was found in CSTR2 compared to CSTR1 with 33%. The investigation showed that dairy manure as inoculum has a marked influence on the start-up period and the biogas production rate. (C) 2017 Elsevier B.V. All rights reserved

Photohydrogen production from dark-fermented palm oil mill effluent (DPOME) and statistical optimization: Renewable substrate for hydrogen

Biological hydrogen production through photo-fermentative process using dark fermented palm oil effluent (DPOME) is a cost effective and environmentally benign process. In this study, effect of various factors like light intensity, agitation rate and dilution of DPOME on the hydrogen productivity of Rhodopseudomanas palustris were investigated using batch system. Investigation methods like response surface methodology (RSM) and Box-Behnken design were employed to investigate the optimum conditions for enhanced photo-fermentative hydrogen production. The regression analysis suggested that hydrogen yield was well fitted by a quadratic polynomial equation (R-2 = 0.92). The hydrogen production was investigated by varying the intensity levels of these three independent variables, in which all have significant influences on hydrogen yield. The set of 19 experimental runs were conducted to optimize these variables. The highest hydrogen yield of 3.07 +/- 0.66 H-2 yield mol-H-2/mol-acetate was obtained under the optimum condition of light intensity 250 W/m(2), agitation rate 200 rpm, and 30% dilution of DPOME. The experimentally obtained hydrogen yield found out to be in a good agreement with predicted yield which was about 2.80 mol-H-2/mol-acetate. In short, results suggest that experimental strategy using RSM approach along with Box-Behnken design can be a promising approach to achieve enhanced biological hydrogen production. (C) 2018 Elsevier Ltd. All rights reserved

Electromagnetic technology on sewage treatment

Magnetic treatments for water and wastewater attract a special attention due to their safety, ecological purity, simplicity and low operating costs. Thus this study was carried out in order to determine the feasibility and effectiveness of applying magnetic technology for a better understanding of the sewage characteristics. The main objectives of this research are to investigate the feasibility of magnetic technology in assisting sedimentation of suspended particles and to understand the mechanism and impact of magnetic application in sewage. The effects of various parameters, magnetic field strength, flow rate, usage of pin-jet and magnetic orientations are used to investigate their effectiveness on the suspended solids removal. A series of electromagnets magnets was used as a reactor in this study and the sewage was taken from Taman Sri Pulai, Johor with estimated PE of 10,300. Experiments indicate that suspended solids removal increases as magnetic field strength and exposure time are increased and flow rate is decreased. It was found out that magnetic field increases the suspended solids removal by 41 percent to 49 percent at 670 Gauss compared to untreated raw sewage. Besides that usage of pin-jet in the magnetically treatment reactors also help to increase another 6 percent of the suspended solids removal. Study carried out also shows that magnetic field enhances the suspended solids removal by accelerating the settling of sludge (settlement time) as well as increasing the sludge density. Hence this technology is definitely beneficial in reducing the volume of sedimentation tank as well as increasing the treatment plant efficienc

Natural organic matter removal from surface water using submerged ultrafiltration membrane unit

This research is conducted to provide quantitative and qualitative integrated understandings of natural organic matter (NOM) fouling characteristics regarding to mechanisms and factors involved, and as well as to develop an optimization works for surface water treatment. In conjunction, a fouling behaviour and autopsy protocol for ultrafiltration membrane fouled with natural organic matter source waters were studied. The Ulu Pontian river, Bekok Dam water and Yong Peng water were used. Fouling characteristics were assessed by filtering the feed water with an immersed ultrafiltration polysulfone and cellulose acetate membranes that were spun by a dry-wet phase inversion spinning process. Relatively hydrophilic NOM source exhibited greater flux decline (72%) but lesser natural organic matter removal (17%) considerably due to pore adsorption, indicating that the low molecular weight (7%>30 kDa), aliphatic linear structure and neutral/base organic matter contained within the hydrophilic fraction were the prime foulants. In contrast, relatively hydrophobic natural organic matter source water that possessed higher charge density (22.63 meq/gC), greater molecular weight (24%>30 kDa) and bulky aromatic structure has shown lesser flux decline (Bekok Dam: 57%) and better NOM rejection (37%) noticeably due to cake deposition, despite filtering through a hydrophobic membrane, suggesting that the electrostatic repulsion was more influential than the steric hindrance. In comparison, a noncharged model compound of similar molecular weight was used to quantify the role of charge repulsion on NOM rejection. However, hydrophobic organic matter source of Yong Peng water has demonstrated the opposite results (flux decline: 77%), presumably due to the governing adsorptive fouling which offsett the electrostatic interactions. Analyses of permeate characteristics revealed that the hydrophobic NOM was preferentially removed by the membrane as opposed to the hydrophilic natural organic matter, hence suggesting that the charge interactions, in addition to size exclusion were more crucial to natural organic matter removal. These findings were consistent with the surrogated and fractionated natural organic matter results, which showed the hydrophilic component exhibiting the highest flux decline (52%) despite lesser dissolved organic carbon (14%) and ultraviolet 254 removal (23%) compared to hydrophobic ( 3 5%) and transphilic fractions (20%). Membrane autopsies analyses confirmed the flux decline results, resistance-in-series and penhleate analyses as membrane was mainly fouled by the hydrophilic natural organic matter rather than humic compounds. Adequacy of the present quadratic models were statistically significant to represent both the natural organic matter removal (R2 =0.966; F=49.36) and membrane permeability (R 2=O.886; F = 13.33). Alum dose exhibited the most significant factor that influenced the natural organic matter removal, followed by the two level interactions of pH and specific ultraviolet absorbance, the main effect of pH, the main effect of specific ultraviolet absorbance, the two level interaction of specific ultraviolet absorbance and alum, the second order effect of specific ultraviolet absorbance and the second order effect of pH. In he case of membrane permeability, the main effect of alum dosage and the second order effect of pH provided the principal effect, whereas the second order effect of alum, the main effect of pH, the two level interaction of pH and specific ultraviolet absorbance provided the secondary effect. Permeate quality surpassing the National Drinking Water Standards was achieved with removal up to 79.50 % of dissolved organic carbon, 87% ultraviolet absorbance, >96% of colour >99% of turbidity and with effective-cost of RM 1.12/M3, suggesting it is cost-competitive compared to conventional water treatment

Novel mesoporous MnCo2O4 nanorods as oxygen reduction catalyst at neutral pH in microbial fuel cells

The aim of this work was to evaluate the comparative performance of hybrid metal oxide nanorods i.e. MnCo2O4 nanorods (MCON) and single metal oxide nanorods i.e. Co3O4 nanorods (CON) as oxygen reduction catalyst in microbial fuel cells (MFC). Compared to the single metal oxide, the hybrid MCON exhibited a higher BET surface area and provided additional positively charged ions, i.e., Co2+/Co3+ and Mn3+/Mn4+ on its surfaces, which increased the electro-conductivity of the cathode and improved the oxygen reduction kinetics significantly, achieved an io of 6.01 A/m2 that was 12.4% higher than CON. Moreover, the porous architecture of MCON facilitated the diffusion of electrolyte, reactants and electrons during the oxygen reduction, suggested by lower diffusion (Rd), activation (Ract) and ohmic resistance (Rohm) values. This enhanced oxygen reduction by MCON boosted the power generation in MFC, achieving a maximum power density of 587 mW/m2 that was ∼29% higher than CON

Microbe-mediated sustainable bio-recovery of gold from low-grade precious solid waste: A microbiological overview

In an era of electronics, recovering the precious metal such as gold from ever increasing piles of electronic-wastes and metal-ion infested soil has become one of the prime concerns for researchers worldwide. Biological mining is an attractive, economical and non-hazardous to recover gold from the low-grade auriferous ore containing waste or soil. This review represents the recent major biological gold retrieval methods used to bio-mine gold. The biomining methods discussed in this review include, bioleaching, bio-oxidation, bio-precipitation, bio-flotation, bio-flocculation, bio-sorption, bio-reduction, bio-electrometallurgical technologies and bioaccumulation. The mechanism of gold biorecovery by microbes is explained in detail to explore its intracellular mechanistic, which help it withstand high concentrations of gold without causing any fatal consequences. Major challenges and future opportunities associated with each method and how they will dictate the fate of gold bio-metallurgy from metal wastes or metal infested soil bioremediation in the coming future are also discussed. With the help of concurrent advancements in high-throughput technologies, the gold bio-exploratory methods will speed up our ways to ensure maximum gold retrieval out of such low-grade ores containing sources, while keeping the gold mining clean and more sustainable

Outlook of fermentative hydrogen production techniques: An overview of dark, photo and integrated dark-photo fermentative approach to biomass

Biomass can be a sustainable choice for bioenergy production worldwide. Biohydrogen production using fermentative conversion of biomass has gained great interest during the last decade. Besides being an efficient transportation fuel, biohydrogen can also be also be a low-carbon source of heat and electricity. Microbes assisted conversion (bioconversion) can be take place either in presence or absence of light. This is called photo-fermentation or dark-fermentation respectively. This review provides an overview of approaches of fermentative hydrogen production. This includes: dark, photo and integrated fermentative modes of hydrogen production; the molecular basis behind its production and diverse range of its applicability industrially. Mechanistic understanding of the metabolic pathways involved in biomass-based fermentative hydrogen production are also reviewed. Keywords: Hydrogen, Biomass, Fermentation, Dark and photo fermentatio

Application of Electroporation Technique in Biofuel Processing

Biofuels production is mostly oriented with fermentation process, which requires fermentable sugar as nutrient for microbial growth. Lignocellulosic biomass (LCB) represents the most attractive, low-cost feedstock for biofuel production, it is now arousing great interest. The cellulose that is embedded in the lignin matrix has an insoluble, highly-crystalline structure, so it is difficult to hydrolyze into fermentable sugar or cell protein. On the other hand, microbial lipid has been studying as substitute of plant oils or animal fat to produce biodiesel. It is still a great challenge to extract maximum lipid from microbial cells (yeast, fungi, algae) investing minimum energy.Electroporation (EP) of LCB results a significant increase in cell conductivity and permeability caused due to the application of an external electric field. EP is required to alter the size and structure of the biomass, to reduce the cellulose crystallinity, and increase their porosity as well as chemical composition, so that the hydrolysis of the carbohydrate fraction to monomeric sugars can be achieved rapidly and with greater yields. Furthermore, EP has a great potential to disrupt the microbial cell walls within few seconds to bring out the intracellular materials (lipid) to the solution. Therefore, this study aims to describe the challenges and prospect of application of EP technique in biofuels processing